1. Field of the Invention
The present invention relates to a process for producing a foaming slag above stainless steel melted in an electric furnace.
2. Discussion of the Background
In the field of melting stainless steel in an electric furnace, the furnace burden of iron scrap, offcuts and ferroalloys is converted into liquid metal by virtue of the generation of electric arcs between the furnace electrodes and said burden.
The production of the steel gives rise to residual products such as dust which is recovered by dust precipitators, approximately 90% of which is recycled in the form of pellets reintroduced into the electric furnace. The remaining 10%, containing too much zinc oxide, is at present stored. The slag is removed after melting.
In the field of melting of nonstainless steels, the principle of foaming slag is based on the reduction of the iron oxide present in the slag. The reduction of the iron oxide is performed by injecting carbon powder into the furnace; a reduction which gives rise to carbon monoxide. The bubbles of carbon monoxide trapped in the molten slag make the latter foam and consequently increase its volume. The slag in foam form coats the end of the electrode and protects the refractories from the electric radiation, and this allows a saving, in the consumption of the electrode, in electricity consumption and in the consumption of the refractories.
In the case of the melting of stainless steels the slag is not sufficiently rich in iron oxide and, as a result, the principle of the foaming slag employed in the production of nonstainless steels is no longer applicable.